A number of industrial and military environments operate under extreme dangers from hydrocarbon fires and the like. For example, military and commercial airplane service and maintenance facilities, chemicals facilities processing flammable liquids such as fuels or the like, and storage or processing facilities for flammable liquids and fuels. In such environments, the existing fire danger creates a need for high speed fire detection and suppression systems. The present systems vary substantially in design. However, all generally utilize one or more detectors together with fire suppressant systems designed to rapidly "flood" the entire area surrounding a suspected fire. The most common type of detectors used are extremely sensitive to energy in the infrared and/or ultraviolet regions of the spectrum. These areas of high sensitivity correspond to the energy emission of a typical hydrocarbon fire. Because of the short interval available for detection of a fire and the distribution of fire suppressant, fire detection systems must operate automatically without the involvement of human operators in the evaluation or decision to disperse fire suppressant.
To meet the needs created for such automatically triggered fire detection and protection systems, practitioners in the art have provided a variety of systems. For example, U.S. Pat. No. 4,775,853 issued to Borruate sets forth a DEVICE AND INSTALLATION FOR THE INSTANTANEOUS DETECTION OF ONE OR MORE PHYSICAL PHENOMENA HAVING A CHARACTER OF RISK in which systems are provided for detection of radiations emitted in the infrared visible and ultraviolet spectra characteristic of risks such as intrusion, fire explosion, leaks of dangerous fluids and electric leaks, disturbances and absence of movement of regular periodic phenomenon. The system comprises a series of filters in combination with a lens and image booster which are coupled to a scanning tube. A preamplifier boosts the signal to sufficient level for operation of a video data processing unit and monitor together with a tape recorder and television telephone transmitter.
U.S. Pat. No. 4,907,281 issued to Hirvonen, et al. sets forth a METHOD OF IMAGE ANALYSIS IN PULVERIZED FUEL COMBUSTION in which an image processing method for flame monitoring is based upon the formation of a video signal characteristic of the combustion process. The flame is monitored by cameras such that the video signal produced thereby defines an average intensity level corresponding to flame characteristics. Other characteristics such as average level may be utilized to define the ignition area.
U.S. Pat. No. 4,074,225 issued to Vandeweghe sets forth an EMERGENCY DETECTION ALARM AND EVACUATION SYSTEM adapted for use in a multi-story building. The systems includes a plurality of spatially distributed fire and smoke detectors and a plurality of exit signaling units for locating the emergency exit doors of the building floor. A control panel in the lobby floor of the building includes lighted indicators which respectively indicate the actuation of particular fire and smoke detectors. Also disclosed is a closed circuit television system for visually monitoring the fire and smoke conditions in selected areas.
U.S. Pat. No. 4,520,390 issued to Paredes, et al. sets forth a BURNER MONITORING SYSTEM in which an array of burners are viewed by a video camera to produce a video signal representing the infrared image of the burner array. Video processing electronics processed the video signal to determine which of the burners is lighted and which is unlighted by the presence or absence of hot spots in the infrared image.
U.S. Pat. No. 4,408,224 issued to Yoshida sets forth a SURVEILLANCE METHOD AND APPARATUS in which an area under surveillance is viewed by a video camera. The image signal from the video camera is converted to data which is stored in a memory. Thereafter, comparison of each new image is carried forward with previous image and an alarm signal generated whenever a difference between successive data images occurs.
U.S. Pat. No. 4,257,063 issued to Loughry, et al. sets forth a VIDEO MONITORING SYSTEM AND METHOD including a television camera scanning the surveilled scenes and means storing a series of image frames. Predetermined areas within the video image are defined for sampling during successive frames. The collection of stored samples is processed to provide a profile of the video signal samples during the frame. Successive frames are then compared to detect differences and trigger alarms in response to predetermined differences.
U.S. Pat. No. 4,112,463 issued to Kammin sets forth a SYSTEM FOR DETECTING A MOTION IN THE MONITORING AREA OF TWO OR MORE TELEVISION CAMERAS in which scenes or objects are monitored and scanned by a plurality of television cameras. The cameras are independent and nonsynchronized with each other. A time division multiplexed image signal derived from the camera signals are stored and compared to subsequently occurring signals to detect changes or motion in the scanned scenes.
While the present systems can quickly detect a fire and trigger the dispersal of fire suppressant chemicals, they are easily fooled by a number of nonfire events. In addition, prior art systems are equally vulnerable to triggering the dispersal of fire suppressant chemicals for trivial or nondangerous fires which might otherwise be easily controlled without the more drastic method of automatic dispersal of fire suppressant chemicals.
In essence, the prior art systems have labored under a basic limitation in that the faster their response time, the more likely they are to be "fooled" by nonfire events. Therefore, the dilemma presented to designers of fire detection and suppression systems is that while fires in such environments have the potential for extreme danger and even catastrophic results and must therefore be controlled and avoided, false alarms and premature or unnecessary triggering of fire suppressant chemical dispersion are costly, damaging and disruptive to operations and therefore must also be avoided. In addition, some fires are trivial or nonthreatening in nature and may be easily controlled by less drastic fire control operations.
The problem presented to fire detection systems is exacerbated by the wide variety of nonfire events which may exist in a fire hazard environment. For example, strong lights, welding units, and objects producing substantial heat such as motors and engines radiate sufficient quantities of ultraviolet and infrared energy to trigger most fire detection systems.
There remains, therefore, a need in the art for a fire detection system which responds quickly and which rapidly determines the existence and degree of a fire. Such systems must be capable of deciding on the appropriate measure to be taken in response to detected fires to avoid false or premature triggering of fire suppressant chemical dispersion.